The present invention relates to an electronic camera which electronically senses an object image and displays and records obtained image information.
In an electronic camera, an object image obtained through an image sensing lens system is photoelectrically converted by a CCD (solid-state image sensing element), sensed by an image sensing circuit, and then converted into a digital image signal by an A/D converter. This digital image signal is subjected to various image processing operations and then displayed on an LCD and recorded on a compact recording medium.
For example, to record an image, the image information of an object image is supplied to an image compression/expansion circuit of, e.g., JPEG (Joint Photographic coding Experts Group) scheme. The JPEG scheme is known well as one of data compression schemes for color still images. This scheme omits specific image information on the basis of the human visual characteristic to reduce the image storage capacity. Image information compressed by the compression/expansion circuit is recorded on a compact recording medium through a predetermined interface.
For such an electronic camera, improvement in image quality is an important subject, and extensive research and development have been made along with an increase in density of solid-image sensing elements and improvement in ability of arithmetic processors.
To improve the image quality, for example, a new dedicated processing system may be added to an electronic camera.
However, popular electronic cameras must meet a very strict cost requirement. Portability is also important. It is not effective to add a large-scale dedicated image processing unit to an electronic camera even if it improves the image quality. This is one of system restrictions according to the characteristic features of an electronic camera in improving it.
Accordingly, this restriction makes it hard to apply, known usual technologies in other technical fields to the electronic camera.
Specifically, it is hard to apply, a new image processing technique in which a pixel at a point is three-dimensionally calculated and interpolated on the basis of neighboring pixels at a plurality of points to the electronic camera. According to image processing of this type, for example, a smooth visual image can be obtained, and the image quality can be greatly improved. This image processing technique is known in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 10-191392. However, the technique disclosed in this prior art assumes use of a special processor called a linear-array-type multi-parallel processor and is not related to application of the image processing technique to an electronic camera.
Demand has arisen for application of such a new image processing technique to an electronic camera under the above-described system restriction.
Conventionally, several techniques have been used to improve the image quality of an electronic camera.
One technique is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-248069. In this technique, to avoid a false signal at an edge portion in pixel interpolation, two images are generated by spatial pixel shift, and a synthesized image thereof is obtained. However, this prior art is different from the new image processing method of three-dimensionally calculating and interpolating a pixel at one point on the basis of neighboring pixels at a plurality of points. This prior art does not disclose a combination of the two techniques.
Another technique is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-108121. This technique obtains a high-quality still image from a recorded moving image in an electronic camera capable of recording/displaying not only a still image but also a moving image. This prior art is also different from the above-described new image processing method of three-dimensionally calculating and interpolating a pixel.